So with a preamp like
the Focusrite ISA 428, which has four instrument inputs AND line in's (not that the lines even enter the mic pre part of the circuit)...
Couldn't you "match" to the hi-z from the line out (where the mix is coming from)? Use two of them and have a dual mono (essentially stereo) mix...
Hmm..
ISA 428
Inputs
* Transformer-based ISA design
* Gain range: Line = +/- 18dB, Mic = 0 to 60dB (both in 6dB steps), Inst = +10 to +40 dB variable
* Input impedance: Line = 10k ohm, Mic = Variable - 600, 2k4 and 6k8 ohm + original ISA 110 settings, Inst = >1M ohm
Analogue Performance
* Noise: Line = -96dB, Mic = -128dB (EIN with 150 ohm input resistance at 60dB of gain)
* THD: Line = 0.003% with 0dBu, 1kHz input and 20Hz to 22kHz band-pass filter, Mic = 0.003%
Analogue Input and Output connectors (balanced)
* D.I inputs: 1/4 inch Jack (unbalanced)
* Mic inputs: XLR (balanced)
* Line: TRS Jack (balanced)
* Insert Sends and Returns: TRS Jack (balanced)
* Additional ADC inputs: XLR (balanced) Line level
* Analogue Outputs: XLR (balanced)
Digital Output Option
* AES/EBU and S/PDIF dual 9-pin D-types
* Optical - ADAT Lightpipe
* Bit depths 16-, 20- or 24-bit
* Frequency options 44.1, 48, 88.2, 96, 176.4 and 192kHz
* Clock options Standard or ?256 x?
* Meter - 0 dBFS = +22dBu
* Digital Performance
* SNR - 120dB A-weighted
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P.S.. I've heard of re'amping, now I'm thinking re-pre'ing sounds interesting...
We've got a Chameleon Labs 7602, that's a Neve 1073 clone..

.. Fat to fatter?
http://www.chameleonlabs.com/product1.htm